Lightning-arrester



(No Model.) 2 Sheets-Sheet 1.

E. THOMSON.

LIGHTNING ARRESTER. No. 454,673. Patented June 23,1891.

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No.- 454,673. Patented June 23,1891.

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WITNESSES.

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UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF SlVAMPSOOTT, MASSACHUSETTS.

LIGHTNING-ARRESTER.

SPECIFICATION forming part of Letters Patent No. 454,673, dated June 23,1891.

Application filed January 31, 1891. Serial No. 379,845. (No model.)

To all whom, it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, in the county of Essex and State ofMassachusetts, have invented a certain new and useful Improvement inLightning-Arresters, of which the following is a specification.

This invention relates to improvements on the type of lightning-arresterforming the subject-matter of my prior application, Serial No. 369,818,filed October 30, 1890.

The present improvements relate to the construction of thelightning-arrester and to the manner of applying it to systems ofdistribution.

In the accompanying drawings, Figures 1,2, and S are diagrams of systemsof distribution having my invention applied thereto. Figs. 3, i, 5, 6,'7, 0, 10, and 11 show various forms of lightning-arresters embodying mypresent improvements.

In Fig. 1, L L represent a line connected to and fed by a dynamo, as atD. This line may be used for feeding lights, motors, or other devices, amotor being shown at M. The line L L may be supposed to be struck bylightning on one or the other of its legs, or at least to be inductivelyacted on, so as to cause a discharge to reach the apparatus supplied byit. In order to protect the dynamo D from such discharge, I establishone of my light ning-protectors 011 each leg or side of the line, as atO 0, each of these consisting of two coils of wire in inductiveproximity or relation, but highly insulated from each other. One ofthese coils is connected into the mainline circuit, and the other isconnected at one end to the main line and at the other end to oneterminal of a suitable discharge device, whose other terminal isconnected to ground. One of these coils is thus in thegenerator-circuit, while the other is in the ground branch, and, asdescribed in my prior application, the action of the coils is such thatwhen a light hing-discharge comes over the line and passes through theground branch coil and dischargeplates to earth it will set up a counterelectro-motive force in the main-line coil, which tends to prevent thedischarge reaching the machine. My present improvement in thisconnection relates to the application of the inductive coil O C on bothsides of the generator, so as to form a double-pole lightningarrester,which shuts off a discharge from either side of the lines. The relationof the turns of the two windings is such as to produce an effectivecounter electro-motive force and will generally be in the relation ofone turn of the ground branch winding to two of the main-line winding;but these windings may be varied as desired. The discharging devicesshown consist of a series of insulating-plates P P, which constitute aseries of spark-discharge spaces, whereby a spark may pass to earthbetween the plates, which are sufficient in number to cut cit anycontinuance of the discharge from the dynamo. The two ground-branchcoils on opposite sides of the generator may be connected to theopposite ends of a single bundle of plates, the middle of the bundlebeing connected to ground, as shown. The ground connection Or should bemade of large surface, so as to be of great carrying capacity for suddendischarge, and of as little self-induction as practicable, and the earthconnection should lead to other extended surfaces of metal buried in theearth. To protect a motor, as at M, the same arrangement may be appliedwith some slight modifications. The connection is made from M throughone winding of coil C to one side of the line L L and through onewinding of coil 0 to the other side. The other windings of these coils(shown in dotted lines) are connected to the two sides of line at points(Z 6 through the discharge-plates P P separated by spaces and havingtheir ground terminals connected together. In this case should thedischarge attempt to reach the motor M from either side of the line oneor the other of the coils O C will come into play, and the discharge isdiverted through the ground-branch winding, setting up an opposin gcounter electro-motivc force in the winding leading to the motor, so asto prevent adischarge from passing thereto. The plates P P P mayrepresent or typify any form of arc-ru pturin g device with s park-gapsbetween the line and earth, and may also represent, as in the figure, aset of separated plates, the separations being quite small, and thenumber of plates being sufficient to provide a succession of arc-spaces,such as to extinguish or prevent the formation of arcs from line to ICOearth. I frequently insert into the line itself, as at 0*, one of thesedouble-wound counterinduetive coils. The ground-branch winding is takenoff from the main line at f and connected to the series ofdischarge-plates P and to ground E through branch G the other winding ofcoil 0 being simply a continuation of the line. A lightning-dischargeoriginating beyond coil 0* willbe diverted through the ground-branchcoil and the discharger P and on its discharge will set up a counterelectro-motive force in the line-winding of coil 0 which prevents thedangerous current from reaching the generator or other apparatus.

Fi 2 shows the same arrangement of my lightning-arrester as in Fig. 1,except that it is here applied toa transformer T used on an alternatingcircuit. The primary lineF F of the transformer is connected to the mainline L L and has inserted in it a coil 0 O 011 each side of thetransformer. One winding of each of these coils is in the primary line.The other winding is connected at a b to the primary line and leads todischarge-plates P P, connected to earth E by wire Gr. The operation issubstantially the same as that above described with regard to Fig. 1.

In Fig. 8 the two coils C O are applied to opposite sides of thegenerator D in a system having a grounded return as, for example, anelectric railway with an overhead line, upon which runs a trolley R, thereturn circuit being supposed to be made to the earth in the ordinaryway. The circuit leads from one pole of the dynamo through one windingof coil 0 to line a and from the other pole of the dynamo through thecorresponding winding of O to earth at b. The other windings of thesetwo coils are connected to the line at a and to the series oflightningarrester plates P and thence to earth. The object'of thisarrangement is to protect the dynamo D from the discharge of a staticcharacter arriving by the earth connection or from the line by settingup a counter-induction in the branch of the circuit or that portion ofthe circuit which leads directly to the dynamo, setting up thisself-induction by virtue of the discharge sent across the plates at P.The motors or other apparatus fed by theline could of course beprotected in the same manner.

Fig. 3 shows the elements of the lightningarrester, L being the line,and a being the point of division of the two windings, which aresupported on a cylinder (1, of insulating material, preferably oneinside and the other outside of said cylinder. It is preferred that theground-branch winding should be placed within the cylinder and theline-winding be wound on the outside of the cylinder. In this figure thedischarging device P is shown as separate from the coil.

In the modification shown in Fig. 6 the earth winding starting at a andpassing through a casing K K, which may be a glass cylinder, isconnected to the bottom of a series of discharge-plates P, while fromthe top plate of the series a connection is carried through aninsulating-tube to the earth connection G and earth-plate E. Theline-winding in this case will be wound on the outside of the glasscylinder K K. The plates P may be separated by air-spaees, or they maybe piled up one above another with layers of insulating material, suchas washers of paper, mica, or other material interposed.

Fig. 7 shows an adjusting device for varying the relative length of theturns of wire in the windings in the coils. As before, the outer windingleading from a to D is in the line-circuit, while the inner winding(shown in dotted lines) is in the ground branch, and there is a handlearranged below provided with a contact for traversing the layers of theinner wire, which may be left bare for the purpose. By this means afraction of a turn or the whole or any portion of the turns may beincluded, as may be required. This gives the power of adjustment to thecoilditions of practice and may be found useful in adapting theapparatus to work under peculiar or special conditions. Of course it isto be understood that the same apparatus for varying the relative numberof turns of the coils might be applied as well to the outer winding asto the inner winding; or, in fact, the same device might be applied toboth windings when it is necessary to make an exact and accuratecompensation for difference of conditions. Any other form of lightningarrester or lightning-discharger may be used in place of plates P P,provided it has means for rupturing the are which would tend to formacross the discharge-spaces. For example, the lightning-arrester shownin Fi 4, consisting of two plates P P in the groundbranch line andprovided with an arc-rupturing magnet N, may be used, and this mag netmay be energized in any suitable manner.

In Fig. 5 I have shown an arrangement whereby there is a separation ofthe eartlv circuit and the line-circuit, and the two circuits or coils,which constitute each one wind ing of the coils O O, are thrown intoinductive relation by a tertiary or third circuit, which consists of asingle winding around each of the coils O 0 connected together, so thata current set up in one will be carried through the other. Thisarrangement, while less effective than that shown in the other figures,could be made to work under limited conditions. A condenser Q could beinterposed in the aforesaid tertiary circuit, as shown in Fig. 10, sothat a current would be carried through by static induction.

Figs. 9 and 11 are intended to exemplify that the two windings of thecoil 0 are not necessarily wound, as above described, but may be laidalongside of one another in any manner provided proper inductiverelations are maintained. Fig. 9 shows a volutewinding, while in Fig.11the Wires are simply laid alongside of each other in elongated fiatcoils.

X'Vhat I claim as new, and desire to secure by Letters Patent, is-

1. The combination, with an electric linecircuit including an apparatusto be protected, of a discharge-circuit shunting such apparatus, andincluding discharging and arc-rupturing devices and inductive devices,respectively, in the line-circuit and shunt :and arranged in inductiverelation to one another, so that the passage of a discharge in theshunt-circuit induces in the line-circuit a counter electro-motive forceopposing the passage of the discharge through the apparatus to beprotected.

2. The combination, with an electric circuit including a dynamo, motor,or other apparatus, of dischargecircuits to ground from each sidethereof, and including inductive devices in inducing relation to eachside of the linecircuit, so as on the passage of a discharge througheither discharge-circuit toset up a counter electro-motive force in thegeneratorcircuit opposing the passage of the discharge to the generator.

3. The combination, with the primary circuit of a transformer, ofdischarge-circuits to ground from both sides of the transformer,including inductive devices in inducing relation to the primary circuiton both sides of the transformer, so as on the passage of a dischargethrough either discharge-eircuit to set up a counter electro-motiveforce in the primary circuit opposing the passage of the discharge tothe transformer.

4. The combination, With an electric circuit including a generator andapparatus supplied thereby, of a discharge-circuit leading to 40 groundat a point distant from the generator, and including an inductive devicein inducing relation to the generator-circuit, so as on the passage of adischarge through the ground branch to set up a counter electromotiveforce in the generator-circuit opposing the passage therein of thedischarge.

5. The combination, with the main circuit and the ground branchcontaining a discharging device, of an inductive apparatus consisting ofan inner coil connected in the ground branch and an outer coil connectedin the main line and an insulating-tube interposed between the twocoils.

6. The combinationpvith a main circuit and a discharging-circuit, of twocoils in inductive relation to one another, one being in the main andthe other in the discharge circuit, and an adjusting device for bringingmore or less of one of said coils into operation.

7. The combination, witha dynamo orother apparatus having one poleconnected to a line and the other to ground, of a discharge-circuit fromthe line through a discharging device to ground, and including inductivedevices in inducing relation to both the line and ground connections ofthe dynamo, so as on the passage of a discharge in the dischargecircuitto set up a counter eleetro-motive force in the generator-circuitopposing the passage of the discharge therein.

In testimony whereof I have hereto set my hand this 23d day of January,1891.

ELIIIU THOMSON. Witnesses:

JOHN W. GIBBONEY, EDWARD M. BENTLEY.

